1. Technical Field
The present invention relates to a light diffusing sheet, more particularly to a light diffusing sheet that includes an organic polymer layer.
2. Description of the Related Art
Research efforts in recent times are focusing more on fine pattern manufacturing, rather than on existing photolithography processes, with the aim of manufacturing fine patterns in the order of micrometers or even nanometers.
In particular, since smaller sizes and high levels of integration of devices in semiconductor processes can reduce times, costs, and sample sizes, and are important for improving new functions, the demand for fine patterns is increasing dramatically. Rapid growth in LED lighting, LED based display devices, OLED lighting, and OLED display devices are also contributing to the demand for light diffusing sheets and light guiding plates.
As such, techniques such as electron-beam (e-beam) lithography, x-ray lithography, etc., for manufacturing fine patterns at the nanometer scale are being researched, with similar methods being used for manufacturing fine patterns at the micrometer scale. However, such processes for manufacturing fine patterns may entail problems such as expensive equipment and long process times. The level of productivity achieved with these methods is extremely low.
Recently, there has been research on improving productivity by using an imprinting process to duplicate patterns with a relatively simple method (S. Y. Chou et al., Appl. Phys. lett., 67: 3114, 1995). There has also been research involving using an elastomeric polymer known as PDMS (polydimethylsiloxane) to fabricate a mold and then coating a wet etching substance or an etching resist substance over an embossed surface and directly printing onto the surface of a secondary substrate to obtain the desired pattern in the secondary substrate or contacting the secondary substrate and filling the mold with a patterning material to create an inverted pattern on the secondary substrate (A. Kumar et al., Acc. Chem. Res., 28: 219, 1995).
Also, there has been disclosed a technique of positioning a polymer mold, which has been duplicated from a silicone mold, over a substrate having a polymer thin film and applying heat so that a polymer pattern may be formed by capillary action (K. Y. Suh et al., Advanced Materials, 13: 1386, 2001).
A technique of adjusting the size of a pattern by using a wet etching method during the transposition of the pattern (C. M. Bruinink et al., Adv. Funct. Mater. 16: 1555, 2006). Here, the polymer pattern is maintained as is and used as an etching resist mask, and a selective etchant is used to alter the size of the pattern being transposed onto the substrate according to the reaction time. However, with wet etching methods, it may be more difficult to finely control the size compared to dry etching methods such as reactive ion etching (RIE), and there is also the drawback of high unit cost associated with preparing molds for various patterns.
Moreover, although methods that do not require photolithography apparatus, such as those using nanoimprinting, microcontact printing using PDMS, and capillary lithography, may be useful for the mass-duplication of one type of fine pattern, these methods entail the difficulty of having to newly fabricate basic design molds when changing the type of pattern is necessary.
Thus, to resolve the problems above, there is an urgent need in the relevant field for technology that allows the production of fine patterns in varying sizes and shapes using simple processes and low costs.